//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5162 SUBJECT: GRB 060526: Swift detection of a burst with x-ray and optical afterglow DATE: 06/05/26 16:45:41 GMT FROM: Scott Barthelmy at NASA/GSFC S. Campana (INAF-OAB), S. D. Barthelmy (GSFC), P. T. Boyd (NASA/GSFC), P. J. Brown (PSU), D. N. Burrows (PSU), J. R. Cummings (NASA/ORAU), C. G. Guidorzi (Univ Bicocca&OAB), S. T. Holland (GSFC/USRA), J. A. Kennea (PSU), C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), A. Moretti (INAF-OAB), K. L. Page (U Leicester), M. Stamatikos (NASA/ORAU), G. Tagliaferri (INAF-OAB) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team: At 16:28:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060526 (trigger=211957). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 232.845, +0.244 {15h 31m 23s, +00d 14' 39"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows multiple peaks starting at T-3 sec out to T+15 sec. The peak count rate was ~2600 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 16:29:43 UT, 73 seconds after the BAT trigger. XRT found an uncatalogued X-ray source located at RA(J2000) = 15h 31m 18.4s, Dec(J2000) = +00d 17' 11.0", with an estimated uncertainty of 6.8 arcseconds (90% confidence radius). This location is 166 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 3.6e-10 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 81 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at (RA,DEC) (J2000) of (232.8265,0.2847) or (15h31m18.36s,+00o17'04.9") with a 1-sigma error radius of about 0.5 arc sec. This position is 6.2 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.6 with a 1-sigma error of about 0.5 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.07. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5163 SUBJECT: GRB 060526: Continued emission for the Swift burst DATE: 06/05/26 17:26:29 GMT FROM: Scott Barthelmy at NASA/GSFC S. Campana (INAF-OAB), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), K. M. McLean (LANL/UTD), A. Moretti (INAF-OAB), M. Stamatikos (NASA/ORAU), G. Tagliaferri (INAF-OAB) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team: Following up the report of the Swift GRB (Campana, et al., GCN 5162), we note that the BAT lightcurve shows a well separated second period of emission starting at ~T+220 sec and lasting until ~T+270 sec. The shape of the emission is FRED-like. Based on the 4-band TDRSS lightcurve, this second emission is significantly softer that the original emission at T+0. Based on initial data we find a refined XRT position of RA(J2000): 15 31 18.27, DEC(J2000): +00 17 07.6, with an error radius of 4.3 arcsec (90% confidence) and 3 arcsec from the previously reported UVOT candidate position. The XRT light curve shows a sharp increase in the count rate starting around T+220 s from burst trigger, approximately coincident with the second BAT peak. As shown in the table below, UVOT sees a fading afterglow in the four finding chart exposures for this burst. In the table, T is the time in seconds since the BAT trigger at the start of the exposure. T Exposure Filter Magnitude 83 100 White 17.6 188 400 V 17.2 866 400 V 17.8 1274 100 White 18.4 We note that the location of this burst is ~11.3 hours from the Sun and therefore well suited for ground-based follow-ups. There is no bright galaxy at this location in the archived SDSS images. We will start receiving the full downlinked data set around 18:00 UT. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5164 SUBJECT: GRB060526 - SDSS Pre-burst Observations DATE: 06/05/26 17:43:57 GMT FROM: Richard J. Cool at U.of AZ/Steward Obs Richard J. Cool (Arizona), Daniel J. Eisenstein (Arizona), David W. Hogg (NYU), Michael R. Blanton (NYU), David J. Schlegel (LBNL), J. Brinkmann (APO), Donald Q. Lamb (Chicago), Donald P. Schneider (PSU), and Daniel E. Vanden Berk (PSU) report: The Sloan Digital Sky Survey (SDSS) imaged the field of burst GRB060526 prior to the burst. As these data should be useful as a pre-burst comparison and for calibrating photometry, we are supplying the images and photometry measurements for this GRB field to the community. Data from the SDSS, including 5 FITS images, 3 JPGS, and 3 files of photometry and astrometry, are being placed at http://mizar.as.arizona.edu/~grb/public/GRB060526 We supply FITS images in each of the 5 SDSS bands of a 8'x8' region centered on the GRB position (ra=232.827 (15:31:18.4), dec=0.286400 (00:17:11.0); GCN 5162), as well as 3 gri color-composite JPGs (with different stretches). The units in the FITS images are nanomaggies per pixel. A pixel is 0.396 arcsec on a side. A nanomaggie is a flux-density unit equal to 10^-9 of a magnitude 0 source or, to the extent that SDSS is an AB system, 3.631e-6 Jy. The FITS images have WCS astrometric information. In the file GRB060526_sdss.calstar.dat, we report photometry and astrometry of 753 bright stars (r<20.5) within 15' of the burst location. The magnitudes presented in this file are asinh magnitudes as are standard in the SDSS (Lupton 1999, AJ, 118, 1406). Beware that some of these stars are not well-detected in the u-band; use the errors and object flags to monitor data quality. In the files GRB060526_sdss.objects_flux.dat and GRB060526_sdss.objects_magnitudes.dat, we report photometry of 1467 objects detected within 6' of the GRB position. We have removed saturated objects and objects with model magnitudes fainter than 23.0 in the r-band. The fluxes listed in GRB060526_sdss.objects_flux.dat are in nanomaggies while the magnitudes listed in GRB060526_sdss.objects_magnitudes.dat are asinh magnitudes. All quantities reported are standard SDSS photometry, meaning that they are very close to AB zeropoints and magnitudes are quoted in asinh magnitudes. Photometric zeropoints are known to about 2% rms. None of the photometry is corrected for dust extinction. The Schlegel, Finkbeiner, and Davis (1998) predictions for this region are A_U=0.337 mag, A_g=0.248 mag, A_r = 0.180 mag, A_i=0.136 mag, and A_z=0.097 mag. The file GRB060526_sdss.spectro.dat contains a list of the 5 objects with SDSS spectroscopy within 6 arcminutes of the GRB position. In addition to the redshift and 1-sigma error for each object, this file also lists the object spectroscopic classification. SDSS astrometry is generally better than 0.1 arcsecond per coordinate. Users requiring high precision astrometry should take note that the SDSS astrometric system can differ from other systems such as those used in other notices; we have not checked the offsets in this region. More detailed information pertaining to our SDSS GRB releases can be found in our initial data release paper (Cool et al. 2006, astro-ph/0601218). See the SDSS DR4 documentation for more details: http://www.sdss.org/dr4. These data have been reduced using a slightly different pipeline than that used for SDSS public data releases. We cannot guarantee that the values here will exactly match those in the data release in which these data are included. In particular, we expect the photometric calibrations to differ by of order 0.01 mag. This note may be cited, but please also cite the SDSS data release paper, Adelman-McCarthy et al. (2006, ApJS, in press, astro-ph/0507711), when using the data or referring to the technical documentation. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5165 SUBJECT: GRB 060526: Watcher Observations DATE: 06/05/26 20:09:37 GMT FROM: John French at UCD,Ireland John French (University College Dublin), Martin Jelinek (IAA Granada), on behalf of the Watcher collaboration report: The Watcher 40cm robotic telescope, located at Boyden Observatory, South Africa, began imaging the field of GRB 060526 (Barthelmy et al., GCN 5162) at 16:29:07, 36.2 seconds after the Swift trigger (19.6 seconds after the GCN notice). Preliminary analysis shows a varying source, consistent with the position of the OT detected in the UVOT observations, with an R-band magnitude of ~15 at T~60s. Analysis is on-going. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5166 SUBJECT: GRB 060526: ROTSE-III Observations of Optical Counterpart DATE: 06/05/26 21:36:39 GMT FROM: Eli Rykoff at U of Michigan/ROTSE E.S. Rykoff (U Mich), S.A. Yost (U Mich), H. Swan (U Mich), W. Rujopakarn (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 060526 (Swift trigger 211957, GCN 5162). The first image was at 17:15:11.1 UT, 2801.1 s after the burst. The unfiltered images are calibrated relative to USNO A2.0. We detect a 17.5th magnitude, fading source with coordinates: 15:31:18.3 +00:17:03.7 (J2000) This is consistent with the Swift/UVOT position reported in GCN 5162. The afterglow did not fade significantly between 2800s and ~6000s post-burst, when it was at ~ 17.5 mag. At 6000s the lightcurve had a break, and started decaying as a smooth power-law with index ~-1. At 13000 s post-burst, the afterglow is at 18.4+/-0.05 mag. Observations are continuing. A jpeg image is available at http://www.rotse.net/images/gsb211957_3c091-100_key.jpg //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5167 SUBJECT: GRB 060526: TNG optical observations DATE: 06/05/26 22:12:02 GMT FROM: Stefano Covino at Brera Astronomical Observatory S. Covino, G.L. Israel, F. Ghinassi, N. Pinilla, on behalf of the CIBO collaboration, report: We observed the optical counterpart of GRB 060526 (Campana et al. GCN 5162; French & Jelinek GCN 5165; Rykoff et al. GCN 5166) with the 3.6m TNG telescope located at the Canary Islands. V and R photometry have been obtained with TNG+DOLoRES. The afterglow is clearly detected at 21:00:56 UT (about 4:32 after the burst) with R = 18.43 +- 0.04, assuming R = 15.0 for the USNO star at RA,DEC 15:31:17.90, 00:15:28.8. Further observations are in progress. This message is citable. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5168 SUBJECT: GRB 060526: Swift/XRT Team refined analysis DATE: 06/05/26 22:53:23 GMT FROM: Sergio Campana at INAF-OAB S. Campana (INAF-OAB), A. Moretti (INAF-OAB), C. Guidorzi (Bicocca Univ. & INAF-OAB), G. Chincarini (Bicocca Univ. & INAF-OAB), D.N. Burrows (PSU) on behalf of the Swift-XRT team report: We have analysed the first orbit of Swift/XRT data of GRB 060526 (Campana et al., GCN 5162 and GCN 5163) summing up 1773 s of data in Photon Counting (PC) and 334 s in Window Timing (WT) mode, respectively. We find a refined XRT position for this burst of: RA(J2000) = 15 31 18.41 Dec(J2000) = +00 17 05.7 with an error of 3.6 arcseconds radius (90% containment). This position is 2.8 arcseconds from the XRT position quoted by Campana et al. (GCN 5163) and 1.1 arcseconds from the UVOT position. The afterglow shows several states: the XRT started observing the GRB at T+73 s. For the first 53 s (up to T+126 s) the XRT remained in WT mode with a slowly decaying count rate (power law decay of -1.4+/-0.9, 90% confidence). Then it switched to PC mode continuing its slow decay up to T+206 s when a bright flare carry back the XRT in WT mode. The flare is made of two flares with FRED-like shape. The first peak reached >335 c/s (being slightly piled-up at level count rate level) around T+240 s and the second about 200 c/s around T+295 s. The decay from the first peak is very steep (as measured from T), with an power law index of -7.7+/-0.7 and also from the second with -8.6+/-0.2. The second flare shows some structures close to the peak. The PC data show the latest stages of the flare and then a break to a much flatter decay (-0.7+/-0.5) around 600 s (further data will improve the determination of the time of this break). This does not allow a first prediction of the flux at one day. From the spectral point of view, PC data before and after the flare are consistent with a simple power law (photon index 1.8+/-0.2) at a column density consistent with the Galactic value NH<1x10^21 cm^-2 (NH_g=6x10^20 cm^-2). Flux in the first WT data is 1.7x10^-10 erg s^-1 cm^-2 (unabsorbed 0.3-10 keV) and in the last PC data 1.6x10^-10 erg s^-1 cm^-2. Considering pre- and post-flare WT and PC data some spectral evolution is observed, this can be explained with a spectral softening or a column density decrease. The spectrum of the first flare (excluded the brightest piled-up portion) is consistent with a simple power law with photon index around 1.8 and a column density larger than the values reported above, likely indicating a fast evolving cut-off power law. The second flare is much softer with with a power law photon index around 2.6. Also in this case the column density is slightly larger than the previous values. Being not piled-up we can estimate a mean 0.3-10 keV unabsorbed flux of 8x10^-9 erg s^-1 cm^-2 (from T+215 to T+304 s). This Circular is an official product of the Swift XRT Team. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5169 SUBJECT: GRB 060526 Lulin optical observation DATE: 06/05/27 02:40:24 GMT FROM: Yuji Urata at Saitama U C. S. Lin, K.Y Huang, W.H. Ip (NCU) Y. Urata (Saitama-U) on behalf of EAFON team report: "We have observed the optical afterglow of GRB 060526 with B and R band using Lulin 1m telescope. After recovery of the weather condition, the first imaging was started at 17:48 UT (1.33 hours after the burst). The afterglow is clearly detected in first image with R = 17.64 +/- 0.05 calibrated relative to USNO-B1.0 catalog. Further analysis is in progress." This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5170 SUBJECT: GRB 060526: Magellan Redshift DATE: 06/05/27 03:25:00 GMT FROM: Edo Berger at Carnegie Obs E. Berger and M. Gladders (Carnegie) report: "We obtained a spectrum of the optical afterglow of GRB 060526 (GCN 5162) with the LDSS3 spectrograph on the Magellan/Clay telescope starting on 2006, May 27.06 UT. The spectrum reveals a strong aborption feature which we identify as Ly-alpha, as well as a large number of aborption features corresponding to SII, SiII, CII, FeII, etc., at a redshift of 3.21. Further analysis is on-going" //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5171 SUBJECT: GRB060526, optical observations DATE: 06/05/27 04:09:52 GMT FROM: Adalberto Piccioni at Astronomy, Bologna U. G. Greco (Bologna University), F. Terra, (Second University of Roma "Tor Vergata"), C. Bartolini, A. Guarnieri and A. Piccioni (Bologna University), D. Nanni (INAF/OAR and Second University of Roma "Tor Vergata"), I. Bruni and S. Galleti (Bologna Observatory), and G. Pizzichini (INAF/IASF Bologna) report: We have imagined the field of GRB 060526 by means of the 152 cm telescope of Loiano equipped with Bfosc obtaining 6 frames in Rc, 3 in V and 3 in I. Preliminary photometry, using USNO B1 (R1) stars, on May 27.0024 (UT mean time) yields Rc = 19.34 +- 0.10. The Rc image has been posted in our public directory from where it can be retrieved by sftp using: hostname: ermione.bo.astro.it username: publicGRB password: GRB_bo. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5172 SUBJECT: GRB060526: Further Swift-UVOT Observations DATE: 06/05/27 04:28:15 GMT FROM: Peter Brown at PSU P. J. Brown (Penn State), S. Campana (INAF-OAB), P. T. Boyd (NASA/GSFC), & F. E. Marshall (NASA/GSFC), report on behalf of the Swift UVOT team: The afterglow of GRB060526 (BAT Trigger 211957) reported in Campana et al. (GCN 5162) is also detected by UVOT in the B filter, as well as the previously reported V and White filters, and continues to fade. We report the following additional UVOT detections: Filter Tstart-Tstop(s) Exp(s) Mag Err White 6335-6534 200 19.2 0.2 V 5311-5511 200 18.2 0.2 V 6744-6944 200 18.6 0.2 B 665-675 10 18.2 0.4 B 6130-6330 200 19.4 0.2 The afterglow is not detected in any filters blueward of B, consistent with the z=3.21 redshift measured by Berger & Gladders (GCN 5170). The 3 sigma upper limits in summed images are: Filter Tstart-Tstop(s) Exp(s) UpperLimit(3sigma) U 641-1492 58 >19.1 W1 617-1468 58 >19.1 M2 593-1444 58 >19.0 W2 693-1554 78 >19.6 In addition, examination of the event mode data of the first V band observation, spanning 188 to 588 seconds after the trigger, shows an optical flare coincident with the flare seen by BAT and XRT (Campana et al. GCN 5163). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5173 SUBJECT: GRB 060526: RTT150 optical observations DATE: 06/05/27 05:16:31 GMT FROM: Rodion Burenin at IKI, Moscow I. Khamitov (TUG), I. Bikmaev, N. Sakhibullin (KSU/AST), Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI) report: We observed the field around position of optical counterpart (Campana et al. GCN 5162; French & Jelinek GCN 5165; Rykoff et al. GCN 5166) of GRB060526 (Swift trigger 211957) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey), starting at May. 27, 00:56UT, i.e. ~5.45 hours after the burst. A series of frames was taken (200*30s exposures in R, 5*300 exposures in B and V). The power-law decay index in Rc is approximately -1.2 between 5.61 and 8.88 hours after the burst. Using USNO-B1 star (RA=15:31:18.6, DEC=+00 17 34.9, R2MAG=16.35) we estimate the following Rc magnitudes for the OT: t-t0 m_R err 5.61 18.840 0.02 5.99 18.893 0.02 6.10 18.924 0.03 6.20 18.908 0.03 6.52 19.029 0.03 6.63 19.051 0.03 6.74 18.977 0.03 7.04 19.133 0.04 7.15 19.141 0.03 7.26 19.128 0.03 7.58 19.173 0.03 7.69 19.291 0.03 7.80 19.283 0.04 8.12 19.243 0.04 8.23 19.409 0.04 8.34 19.342 0.04 8.45 19.406 0.05 8.56 19.290 0.05 8.66 19.270 0.04 8.77 19.377 0.06 8.88 19.477 0.06 The Rc lightcurve can be found at: http://hea.iki.rssi.ru/grb/060526/lc.jpg This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5174 SUBJECT: GRB 060526: Refined analysis of the Swift-BAT burst DATE: 06/05/27 17:51:50 GMT FROM: Scott Barthelmy at NASA/GSFC C. Markwardt (GSFC/UMD), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/ORAU), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), M. Koss (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/JSPS/USRA), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-119 to T+1000 sec from recent telemetry downlinks, we report further analysis of BAT GRB 060526 (trigger #211957) (Campana, et al., GCN 5162 & 5163). The BAT ground-calculated position is RA,Dec = 232.838,+0.292 deg {15h 31m 21.0s,+0d 17' 32.9"} (J2000) +- 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 61%. As noted in GCN 5163, there are two well separated episodes of emission detected in the BAT instrument. The initial emission contains two FRED-like peaks, the first starting at T-3sec, peaking at T+1, and ending at T+5 sec; and the second starts at T+6 sec, peaks at T+7 sec, and returns back to the background level at T+13 sec. T90 (15-350 keV) for this first episode is 13.8 +- 2 sec (estimated error including systematics). The scond episode consists of a single symmetric peak at T+250 sec (230 to 270 sec). This second episode is coicident with the XRT flare described in GCN 5168. For the first episode, the time-averaged spectrum from T-1.3 to T+17.0 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.66 +- 0.20. The fluence in the 15-150 keV band is 4.9 +- 0.6 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.17 sec in the 15-150 keV band is 1.7 +- 0.2 ph/cm2/sec. For the second episode, the time-averaged spectrum from T+230 to T+270 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.07 +- 0.18. The fluence in the 15-150 keV band is 5.9 +- 0.6 x 10^-7 erg/cm2. This is slightly more fluence than the first episode, but only about half the peak flux. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5175 SUBJECT: GRB 060526: MDM-2.4m Observations DATE: 06/05/27 18:38:09 GMT FROM: Xinyu Dai at Ohio State U N. D. Morgan and X. Dai (Ohio State Univ.) We observed GRB 060526 (GCN 5162, Campana et al. 2006) with MDM-2.4m for three epochs. The afterglow is detected in all three observations. Using USNO B-1 star as the reference (RA=15:31:18.6, DEC=+00 17 34.9, R2MAG=16.35, same one used in GCN5173 Khamitov et al. 2006), we get Rc = 19.90 @ May 27, 03:33:00 UT Rc = 19.98 @ May 27, 06:02:00 UT Rc = 20.11 @ May 27, 09:49:00 UT This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5176 SUBJECT: GRB 060526: Optical Flare DATE: 06/05/27 23:08:55 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern (Columbia U.), E. Armstrong (UCSD), & N. Mirabal (U. Michigan) report on behalf of the MDM Observatory GRB follow-up team: "Using the MDM 1.3m telescope on Kitt Peak, we obtained a continuous R-band time series of the afterglow of Swift GRB 060526 (Campana et al. GCN 5162), consisting of 40 10-minute exposures, from 11.0 to 18.2 hours after the burst. Preliminary photometry was performed using comparison stars in r' from the SDSS calibration (Cool et al. GCN 5164). In addition, wherever possible, we placed other GCN reported R-band photometry (Covino et al. GCN 5167; Khamitov et al. GCN 5173; Morgan & Dai GCN 5175) on a common scale using the SDSS r' magnitudes of their indicated comparison stars. As a result, we find that a power-law decay index of -1.18 +/- 0.05 fitted to the Khamitov et al. data alone from 5.6 to 8.9 hours also fits the MDM light curve very well, until about 16 hours after the burst. At that time, a flare began that had a rise time of about 40 minutes, followed by a slower decay, and had not yet returned to the extrapolated power law when the observations were terminated at twilight. The peak of the flare occurred around May 27 09:06 UT, and reached about 0.3 magnitudes above the extrapolation. In combination with the multiple episodes of gamma-ray and X-ray emission (Campana et al. GCNs 5163, 5168; Markwardt et al. GCN 5174) and the long plateau in the early optical light curve (Rykoff et al. GCN 5166), these results indicate the possibility of extended and complex activity from GRB 060526 that warrants intensive monitoring. A preliminary version of the MDM optical light curve and incorporated GCN data is available at http://www.astro.columbia.edu/~jules/grb/060526/ The data contained in the figure are not yet suitable for publication." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5177 SUBJECT: GRB 060526: RTT150 optical observations, afterglow flattening DATE: 06/05/28 15:00:31 GMT FROM: Irek Khamitov at TUG I. Khamitov (TUG), I. Bikmaev, N. Sakhibullin (KSU/AST), Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI) report: We observed the field around position of optical counterpart of GRB060526 (Campana et al. GCN 5162; French & Jelinek GCN 5165; Rykoff et al. GCN 5166) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey). The observations were made in BVR in two epochs: May. 27, 18:40UT and 23:20UT (26.19 and ~30.86 hours after the burst). The afterglow is detected clearly in VRc bands and marginally in B. Using Landolt standards we calibrate reference star used in our GCN 5173 and estimate its Rc magnitude as 16.484+/-0.01, 0.13 mag fainter then R2MAG of USNO-B1. We estimate the following Rc magnitudes for the OT: t-t0 m_R err 26.31 20.581 0.04 31.57 20.641 0.04 These magnitudes significantly deviates from power-law decay with index -1.2. The flare detected by Halpern et al. (GCN5176) is continued by the flattening of afterglow light curve. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5178 SUBJECT: GRB 060526: REM observations DATE: 06/05/28 15:30:01 GMT FROM: Stefano Covino at Brera Astronomical Observatory L. Calzoletti, L.A. Antonelli, S. Covino, E. Molinari, G. Chincarini, F.M. Zerbi, V. Testa, G. Tosti, F. Vitali, P. Conconi, G. Cutispoto, G. Malaspina, L. Nicastro, E. Palazzi, E. Meurs, P. Goldoni, on behalf of the REM/ROSS Team, report: We observed the field of GRB 060526 (Campana et al. GCN 5162) with the robotic 60 cm REM telescope located at La Silla ESO Observatory (Chile). The GRB was not visible from La Silla at the trigger time and REM started acquiring automatically a set of infrared images (J,H,K filters) at 23:08:56 UT (about 6.67 hours after the burst) when the target became visibile. The integration time was 100s in each filter. A second set of images was taken starting at 03:56:19 UT with the same observing setting. The analysis of both dataset do not show any infrared source at the position of the optical afterglow (Rykoff et al. GCN 5166, Campana et al. GCN 5168) down to the 3-sigma upper limit magnitudes J=16.5, H=16.2, K=15.8. This message may be cited. [GCN OPS NOTE(29may06): Per author's request, the starting time for the images was changed from "16:28:30" to "23:08:56".] //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5179 SUBJECT: GRB060526: possible break in the optical light curve DATE: 06/05/28 17:07:23 GMT FROM: Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr Christina C. Thoene, Johan P.U. Fynbo (DARK Cosmology Centre), Uffe G. Joergensen (NBI Copenhagen) report: We observed the OT of GRB060526 (GCN 5162, GCN 5166) with the Danish 1.54m telescope and DFOSC on La Silla in the R-band at several epochs on May 26 and May 27. A fit to our data from the first night gives a powerlaw decay with a temporal decay index of 0.86, whereas the data obtained at the second night are well fitted by a powerlaw with index 1.73. Therefore, in contrast to the flattening reported in GCN 5177, we observe a considerable steepening of the lightcurve between the first and the second night and a possible break between the two nights. A plot of the data and fit is available at: www.astro.ku.dk/~cthoene //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5180 SUBJECT: GRB 060526: SMARTS optical/IR afterglow observations DATE: 06/05/28 19:11:24 GMT FROM: Bethany Cobb at Yale U B. E. Cobb (Yale), part of the larger SMARTS consortium, reports: Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 060526 (GCN 5162, Campana et al.) with a mid-exposure time of 2006-05-27 01:13 UT (~8.7 hours post-burst) and again at 2006-05-27 04:07 UT (~11.6 hours post-burst). Total summed exposure times for each observation amounted to 36 minutes in I and 30 minutes in J. The afterglow of GRB 060526 is visible in each combine image. The preliminary magnitudes reported below were calibrated using several USNO-B1.0 stars in the I-band and two 2MASS standards in J. [The errors on the photometric calibration are ~0.2 in I and ~0.02 in J; these errors are in addition to the statistical errors listed below.] time post-burst I magnitude J magnitude ------------------------------------------------------ 8.7 hours 18.99 +/- 0.02 18.16 +/- 0.06 11.6 hours 19.31 +/- 0.02 18.58 +/- 0.07 The afterglow decay index is constrained by our observations to be alpha = 1.2 +/- 0.2 from 8.7 to 11.6 hours post-burst. This value is in agreement with the decay value from 5 to 16 hours post-burst reported by Khamitov et al. (GCN 5173) and Halpern et al. (GCN 5176). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5181 SUBJECT: GRB060526: optical observations DATE: 06/05/28 21:42:04 GMT FROM: Alexei Pozanenko at IKI, Moscow V.Rumyantsev (CrAO), A. Pozanenko (IKI) on behalf of larger GRB follow up collaboration report: We observed optical transient of GRB060526 (Campana et al. GCN 5162, French & Jelinek GCN 5165, Rykoff et al. GCN 5166) with the Shajn 2.6m telescope of CrAO between May 27 (UT) 18:27 - 20:05 in R and B bands. In combined images we detect OT in R and do not detect it in B-band. The photometry of the OT and upper limits are following: Mid time Filter Exp. OT, mag. Limiting mag. (UT) sec May 27.803 R 18x60 20.25 +/-0.04 23.0 May 27.777 B 6x120 - 20.6 The photometry calibration is based on USNO A2.0 field stars. (We note that R magnitudes of field stars in USNO A2.0 are somewhat brighter (~0.2m) than those in USNO B1.0). The R-combined image can be found in http://grb.rssi.ru/GRB060526 This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5182 SUBJECT: GRB 060526: Tautenburg OT observation and light curve fitting DATE: 06/05/29 02:41:31 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann & C. Hoegner (Thueringer Landessternwarte Tautenburg) report: The afterglow of GRB 060526 (Campana et al., GCN 5162) was observed with the Tautenburg 1.34m Schmidt telescope in the R band in inclement conditions (passing clouds). A total of four 600 sec exposures were obtained, each significantly deeper than the DSS. The afterglow is detected in each image. We measure the magnitude from a stack of all four images, using the magnitude Khamitov et al. (GCN 5177) derived for the USNO star at RA=15:31:18.6, Dec=+00:17:34.9 (R=16.848): Epoch dt (days) Rc dRc 28.9768 2.2904 21.55 0.13 We collect data from Rykoff et al. (GCN 5166), Covino et al. (GCN 5167), Greco et al. (GCN 5171), Khamitov et al. (GCN 5173), Morgan & Dai (GCN 5175), Khamitov et al. (GCN 5177), Thoene et al. (GCN 5179) and Rumyantsev & Pozanenko (GCN 5181). This data set can be fit by a single power law with slope alpha = 0.99 +/- 0.01, starting at 6000 seconds after the burst (Rykoff et al., GCN 5166). But we find significant deviations from the power law, as high as 0.3 mags above and below (cf. Halpern et al., GCN 5176) the fit, leading to a high chi^2. This behaviour is reminiscent of GRBs 021004 and 030329. For the data beyond 1.3 days, we find alpha = 1.64 +/- 0.17, in agreement with Thoene et al. (GCN 5179). Our data can not rule out that a break in the light curve has occured, lying well on the extrapolation of the data of Thoene et al. (GCN 5179). If so, the post jet-break decay slope is very shallow. The afterglow is thus well-suited for further follow-up, and dense R band imaging is encouraged. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5183 SUBJECT: GRB 060526: RTT150 optical observations DATE: 06/05/29 05:42:12 GMT FROM: Rodion Burenin at IKI, Moscow I. Khamitov (TUG), I. Bikmaev, N. Sakhibullin (KSU/AST), Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI) report: We observed the field around position of optical counterpart of GRB060526 (Campana et al. GCN 5162; French & Jelinek GCN 5165; Rykoff et al. GCN 5166) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe,TUBITAK National Observatory, Turkey). The observations were made in Rc in two epochs: May 28, 20:07UT and May 29, 00:53UT (~51.64 and ~56.41 hours after the burst). The afterglow is detected clearly in Rc bands in both epochs. We estimate the following Rc magnitudes for the OT: t-t0 m_R err 51.64 21.464 0.04 56.41 21.816 0.05 The last value indicates that the afterglow light curve had returned to the extrapolated power-law decay with index -1.2 which was found between 5 and 16 hours of post-burst reported by Khamitov et al. (GCN 5173), Halpern et al. (GCN 5176) and Cobb et al. (GCN 5180). Our Rc lightcurve can be found at: http://hea.iki.rssi.ru/grb/060526/lc_0528.jpg This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5185 SUBJECT: GRB060526: Optical counterpart from MIRO DATE: 06/05/30 03:02:47 GMT FROM: Kiran S Baliyan at Physical Research Lab, Ahmedabad,India K.S. Baliyan, S. Ganesh, H.O. Vats and J.K. Jain (MIRO-PRL, Ahmedabad, India) report: We observed the field around position of the optical counterpart of GRB060526 (Campana et al. GCN 5162, 5163; French & Jelinek GCN 5165; Rykoff et al. GCN 5166) beginning at 21:02 UT. The 1296*1154 CCD mounted on the 1.2 M telescope of Mt Abu IR Observatory, operated by Physical Research Laboratory, Ahmedabad- India, was used to observe OT in VRI bands with 180 second exposures. The afterglow is detected clearly in all the bands. We use Rc=16.484+/-0.01 mag for USNO B-1 star (RA=15:31:18.6, DEC=+00 17 34.9) as reference value to estimate preliminary R magnitudes for OT on May 26: 21:02:59 UT 18.65 +/- 0.19 21:09:26 UT 18.71 +/- 0.32 21:32:38 UT 19.06 +/- 0.19 22:44:22 UT 19.19 +/- 0.24 This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5186 SUBJECT: GRB 060526: RTT150 optical observations DATE: 06/05/30 05:05:45 GMT FROM: Rodion Burenin at IKI, Moscow I. Khamitov (TUG), I. Bikmaev, N. Sakhibullin (KSU/AST), Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI) report: We observed the optical counterpart of GRB060526 (Campana et al. GCN 5162; French & Jelinek GCN 5165; Rykoff et al. GCN 5166) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe,TUBITAK National Observatory, Turkey), starting at May. 29, 18:44UT, i.e. ~74.26 hours after the burst. A series of frames were taken. The afterglow is detected in Rc band and marginally in V. We estimate the following Rc magnitudes for the OT: t-t0 m_R err 76.03 22.19 0.07 78.13 22.31 0.07 80.40 22.45 0.12 These points lie approximately on the extrapolation of the first day power law decay (e.g., Khamitov et al., GCN 5173). Our Rc lightcurve can be found at: http://hea.iki.rssi.ru/grb/060526/lc_0529.jpg This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5187 SUBJECT: GRB060526: afterglow fitting and probable jet break DATE: 06/05/30 16:43:38 GMT FROM: Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr D. A. Kann (TLS Tautenburg) and C. C. Thoene (DARK Cosmology Center) report: Gathering further data from the GCN (Khamitov et al., GCN 5183, 5186, Baliyan et al., GCN 5185) in addition to those referenced in Kann & Hoegner (GCN 5182), we perform fits to the R afterglow light curve. A single power law fit to all data beyond 6000 seconds yields alpha = 1.04 +/- 0.01, but the late-time data beyond two days lie significantly beneath the fit. A broken power law gives a better fit, with alpha_1 = 0.98 +/- 0.10, alpha_2 = 2.06 +/- 0.13, and break time t_b = 1.76 +/- 0.1 days. The break smoothness parameter n is fixed to 10. Still, the fit is not acceptable, with strong deviations around 0.5 days. Fitting separate parts of the light curve, we find a better fit with a double broken power law. The first part (0.19 to 1.1 days) is described by alpha_1 = 1.35 +/- 0.07, alpha_2 = 0.85 +/- 0.08 and t_b = 0.44 +/- 0.08 days, n = -10 fixed. The fit is marginally acceptable, with deviations due to scatter (different zero points and comparison stars). The second part (0.53 days to the end) is described by alpha_1 = 0.76 +/- 0.04, alpha_2 = 1.87 +/- 0.07 and t_b = 1.42 +/- 0.08 days, n = 10 fixed. This fit is acceptable. Alpha_2 of the first part and alpha_1 of the second part are identical within errors, as expected. We note that the extension of this last fit to early times is consistent with the first ROTSE data point (Rykoff et al., GCN 5166) and marginally consisten with the very early Watcher data (French & Jelinek, GCN 5165). This strengthens the picture that the break first described by Thoene et al. (GCN 5179) is the jet break. The post-break decay is relatively smooth. We caution that these fits do not include the dense data set presented by Halpern, Armstrong & Mirabal (GCN 5176) and the optical flare they detected. Similar to early fits of GRB 030329 presented in the GCN, these fits may be the result of inhomogenous coverage of a highly variable light curve. Further deep monitoring is encouraged. The plots for the double broken power law fits can be found at www.astro.ku.dk/~cthoene //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5188 SUBJECT: GRB 060526: Multiple Optical Flares DATE: 06/05/30 21:34:18 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern (Columbia U.), E. Armstrong (UCSD), & N. Mirabal (U. Michigan) report on behalf of the MDM Observatory GRB follow-up team: "We have continued to observe the afterglow of Swift GRB 060526 (Campana et al. GCN 5162) in the R-band for four consecutive nights using the MDM 1.3m. In combination with the GCN reported R-band photometry of Khamitov et al. (GCNs 5173,5177,5183,5186), it is evident that there have been at least four flares, by which we mean alternating positive and negative deviations from a mean decay rate. These are characterized as increases and decreases of at least 0.3 mag in as short a time as delta t = 0.04*(t-t0), where t0 is the burst time. In view of these flares, it is problematic to fit a small number of power-law segments (as noted by Kann & Thoene GCN 5187). Rather, we observe that the most recent point, r' = 22.87+/-0.07 on May 30 04:23 UT as calibrated with Cool et al. (GCN 5164) data, falls only 0.25 mag below the -1.18 power law originally fitted from 5.6 to 16 hours by Khamitov et al. (GCN 5173) and Halpern et al. (GCN 5176). Other details of the MDM optical light curve and incorporated GCN data can be seen at: http://www.astro.columbia.edu/~jules/grb/060526/ This type of light curve is not uncommon in GRB afterglows (see, e.g., Stanek et al. astro-ph/0602495, and references therein), and is often apparent when the source is well placed for long observing runs at ground-based telescopes." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5189 SUBJECT: GRB 060526: RTT150 optical observations DATE: 06/05/31 06:17:36 GMT FROM: Rodion Burenin at IKI, Moscow I. Khamitov (TUG), I. Bikmaev, N. Sakhibullin (KSU/AST), Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI) report: We continue our observations of the optical counterpart of GRB060526 (Campana et al. GCN 5162; French & Jelinek GCN 5165; Rykoff et al. GCN 5166) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe,TUBITAK National Observatory, Turkey). A series of frames were taken on May 30. The afterglow is detected on combined images in both V and R bands. We estimate the following Rc magnitudes for the OT: t-t0 m_R err 104.05 23.14 0.09 Our Rc lightcurve can be found at: http://hea.iki.rssi.ru/grb/060526/lc_0530.jpg In combination with MDM 1.3-m observations (Halpern et al., GCN 5188) these data suggest that the OT light curve can not be fitted by a combination of power laws and contain several optical flares. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5192 SUBJECT: GRB060526, optical observations DATE: 06/05/31 18:48:03 GMT FROM: Adalberto Piccioni at Astronomy, Bologna U. F. Terra (Second University of Roma "Tor Vergata"), G. Greco, C. Bartolini, A. Guarnieri, A. Piccioni (Bologna University), D. Nanni (INAF/OAR and Second University of Roma "Tor Vergata"), I. Bruni, S. Galleti (Bologna Observatory) and G. Pizzichini (INAF/IASF Bologna) report: "We observed the field of GRB 060526 (Campana et. al., GCN 5162) with the 152 cm Cassini Telescope located in Loiano, equipped with BFOSC in the nights april 26-27 (seeing 2".0) and 27-28 (seeing 1".7). The photometry is based on the SDSS stars (Cool et al. GCN 5164) and trasformation derived from Lupton (2005). Using this transformation we find for the USNO B-1 star (RA = 15 31 18.6, DE = +00 17 34.9) the magnitude Rc = 16.50, consistent with the calibration of Khamitov et al. (GCN 5177). We find the following magnitudes: Mean...UT .......Filter........Exptime (s).......magnitude May...26.908........Rc............900............18.85+/-0.08 May...26.921........Rc............900............18.92+/-0.07 May...26.935........V............1200............19.37+/-0.08 May...26.949........I.............900............18.60+/-0.06 May...26.961........Rc............900............19.08+/-0.07 May...26.975........V............1200............19.64+/-0.09 May...26.990........I.............900............18.80+/-0.06 May...27.002........Rc............900............19.28+/-0.09 May...27.017........V............1200............19.79+/-0.11 May...27.031........I.............900............18.94+/-0.08 May...28.002........Rc............900............20.61+/-0.13 May...28.017........Rc............900............20.44+/-0.10 //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5193 SUBJECT: GRB 060526: RTT150 optical observations DATE: 06/06/01 11:35:00 GMT FROM: Rodion Burenin at IKI, Moscow I. Khamitov (TUG), I. Bikmaev, N. Sakhibullin (KSU/AST), Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI) report: We continue our observations of the optical counterpart of GRB060526 (Campana et al. GCN 5162; French & Jelinek GCN 5165; Rykoff et al. GCN 5166) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe,TUBITAK National Observatory, Turkey). A series of frames were taken on May 31. The afterglow is detected on combined images in both V and R bands. We estimate the following Rc magnitudes for the OT: t-t0 m_R err 125.74 23.69 0.19 Our Rc lightcurve can be found at: http://hea.iki.rssi.ru/grb/060526/lc_0531.jpg This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5194 SUBJECT: GRB 060526: Break in X-ray light curve DATE: 06/06/01 18:54:41 GMT FROM: David Burrows at PSU/Swift A. Moretti (INAF-OAB), D.N. Burrows (PSU) , S. Campana (INAF-OAB), G. Chincarini (UNIMIB, INAF-OAB), and G. Tagliaferri (INAF-OAB) report on behalf of the Swift XRT team: We have analyzed six days of Swift XRT data from GRB 060526 (Campana et al., GCN5162), with a total exposure of 70ks. After the flaring episodes between 200s and 400s interval from the trigger, already reported in Campana et al. (GCN 5168), the light curve presents a shallow decay with slope -0.7(+-0.1) until (1.1+-0.3)e5 seconds after the trigger (1.2+-0.3 days). Superimposed on the shallow decay a small bump is present at 7 ks. At (1.1+-0.3)e5 seconds the light curve breaks to a much steeper slope of (-2.8+-0.1). We note that this slope is very similar to the optical decay slope of the last five data points obtained by the RTT150 telescope (Khamitov et al., GGNs 5186, 5189, and 5193, slope ~ -2.75), and that the X-ray break time also seems to correspond roughly to a break in the general trend of the optical light curve (e.g., Thoene et al., GCN 5179; Kann and Hoegner, GCN 5182; Kann and Thoene, GCN 5187; although the slopes reported in these circulars are shallower than those seen in the XRT light curve and in the last 5 RTT150 data points). On the other hand, the optical light curve is quite complex (Halpern, Amstrong, and Mirabel, GCNs 5176, 5188). If interpreted as a jet break, the jet opening half-angle for this burst is about 4.7 degrees x (Eiso/10^53)^(-1/8) x (n/10 cm^-3)^(1/8). Using the total BAT fluence, we obtain Eiso = 2.3e52 ergs (15-150 keV observed frame), which would correspond to 5.6 degrees for the jet opening angle. We did not extrapolate Eiso into the usual energy band due to the limited energy range of the BAT and the single power law fit to the BAT spectrum, but we expect that the jet angle should be in the range of 4-5 degrees. A lower density would reduce this angle. This Circular is an official product of the Swift XRT Team. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5202 SUBJECT: GRB 060526: Tautenburg Second Epoch Observations DATE: 06/06/03 01:53:49 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann and U. Laux (Thueringer Landessternwarte Tautenburg) report: We observed the location of the afterglow of GRB 060526 (Campana et al., GCN 5162) with the Tautenburg 1.34m Schmidt telescope. Observing conditions were mediocre. While it was clear, transparency was low and sky background was high due to moonlight and light pollution. We obtained 20 x 600 sec exposures for a total integration time of 12000 seconds. Observations commenced on June 2, 21:04:17 UT and ended June 3, 00:55:07 UT. Midexposure time is June 2.9546, which is 7.2682 days after the burst. We do not detect the optical afterglow. Using the USNO calibration star from Khamitov et al., GCN 5177, we derive the following 2 sigma limiting magnitude: t-t_0 Rc limit 7.2682 > 23.5 As Khamitov et al. (GCN 5193) already found a similar magnitude of the afterglow two days earlier, this limit can only constrain that no further very bright flares have occured. No further observations are planned. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5266 SUBJECT: GRB060526: optical observations DATE: 06/06/16 17:06:26 GMT FROM: Alexei Pozanenko at IKI, Moscow D. Sharapov (MAO and NOT, La Palma), T. Augusteijn (NOT, La Palma), A.Pozanenko (IKI), V.Rumyantsev (CrAO) on behalf of larger GRB follow up collaboration report: We observed the error box of GRB060526 (Campana et al. GCN5162) in Nordic Optical Telescope with ALFOSC between (UT) June 05 23:37 and June 06 00:41. We do not detect the optical afterglow. Limiting magnitude of a combined image of total exposure 10x300 is R~ 24.6. Based on last 3 points of TT150 (Khamitov et al. GCNs 5186, 5189, 5193) the limiting magnitude R=24.6 at mid time (UT) June 06.0125 (T0+10.486d) is compatible with X-ray power law decay index 2.8+/-0.1 (Moretti et al., GCN5194). While no sources are detected within refined XRT error circle (Campana et. GCN5168) faint galaxy (R=24.4 +/- 0.3) is detected at (J2000) RA = 15:31:18.2 Dec = +00:17:12.7. Taking into account redshift of the OT of GRB060526 z=3.21 (Berger and Gladders GCN5170) it is unlikely that the detected galaxy is connected with GRB060526. The combined image can be found at http://grb.rssi.ru/GRB060526/ //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5306 SUBJECT: GRB060526: optical observations DATE: 06/07/13 14:05:29 GMT FROM: Alexei Pozanenko at IKI, Moscow V.Rumyantsev (CrAO), A.Pozanenko (IKI), M.Ibrahimov, I.Asfandyarov (MAO) on behalf of larger GRB follow up collaboration report: We observed the afterglow of GRB060526 (Campana et al. GCN5162) in Maidanak Astronomical Observatory (MAO) with 1.5 m telescope in R and B-passbands on May 26-31, and June 1-2. Additinnaly we recalibrated observation with CrAO Shajn 2.6m telescope (Rumyantsev et al. GCN5181). A photometry is based on the star USNO B1.0 RA=15 31 18.60 DEC=+00 17 35.00 R2=16.35 B2=16.42 already used in GCNs (Khamitov GCN5173, Morgan GCN5175, Kann GCN5172, Baliyan GCN5185). R-band photometry of the afterglow and upper limits are following: Mid_time (UT), Telescope, R_mag 26.7778 MAO1.5 17.98 +/- 0.01 26.7829 MAO1.5 18.06 +/- 0.01 26.7883 MAO1.5 18.11 +/- 0.01 27.7799 CrAO2.6 20.38 +/- 0.07 27.8143 CrAO2.6 20.47 +/- 0.06 27.8233 MAO1.5 20.43 +/- 0.04 28.8014 MAO1.5 21.31 +/- 0.13 29.8053 MAO1.5 22.06 +/- 0.11 30.8049 MAO1.5 22.84 +/- 0.24 31.7938 MAO1.5 23.52 +/- 0.32 01.8318 MAO1.5 >23.6 02.8648 MAO1.5 >23.8 The afterglow is clearly detected in B-filter up to May 29; B-photometry is underway. The message may be cited.